Hydraulic restraining mechanism for free-piston units



Jan. 21, 1947. A. KALITINSKY 1 V I HYDRAULIC RESTRAINING MECHANISM FDR FREE-PISTON UNITS Fi'led Nov. '6, 1944 2 Sheets-Sheet 1 FIG. I

INVENTOR Jan. 21, 1947. A. KALITIN SKY 2,414,745

HYDRAULIC RESTRAINING MECHANISM FOR FREE-PISTON UNITS Filed Nov. 6, 1944 2 Sheets-Sheet 2 FIG. 2

'INVENTOR Patented Jan. 21, 1947 HYDRAULIC RESTRAINING MECHANISM FOR FREE-PISTON UNITS Andrew Kalitinsky, Eagleville, Conn.,

United Aircraft Corporation,

assignor to East Hartford,

Conn., a corporation of Delaware 6, 1944, Serial No. 562,250

Application November 8 Claims.

The opposed pistons of a free piston engineand-compressor unit have been maintained always at equal distances from the center of the engine by restraining devices interconnecting the pistons. The linkage devices have been, in general, of two types. One type uses a rocking lever with its ends connected by rods to the pistons. The other type uses a pinion engaging racks on a pair of rods extending from the pistons, A feature of this invention is a hydraulic restraining device to avoid a mechanical connection between the pistons. The fluid which is moved within the mechanism as the pistons reciprocate forms a part of the moving mass of the unit. As the rate of piston reciprocation is dependent upon the moving mass, a large quantity of fluid reduces this rate. A feature of this invention is a fluid actuated restraining mechanism which has a relatively small quantity of fluid moved by the pistons.

Another feature is an arrangement for moving both pistons into symmetry when the compressor is stopped.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate what is now considered to be a preferred embodiment of the invention.

Fig. 1 is a sectional view through the unit.

Fig. 2 is a diagrammatic view, on a larger scale, of the restraining mechanism.

The unit shown includes an engine cylinder l8 having reciprocating pistons 12 and I4 to which compressor pistons l6 and IS in cylinders 28 and 22 are integrally connected. Sleeves 24 and 26 attached to the compressor pistons complete the reciprocating piston assemblies. The sleeves in combination with stat onary pistons 28 and 38 form air spring cylinders.

The piston assemblies are moved apart by the burning of fuel by the engine cylinder. Air compressed in the air spring cylinders on the power stroke returns the piston assemblies.

Intake manifold 34 conducts air to intake valves 38 through which air automatically enters opposite ends of the compressor cylinders. The compressed air leaves the cylinders through discharge valves 38, also at opposite ends of the compressor cylinder, and passes through scavenge manifold 40 and through ports 42 and 44, which are uncovered by pistons l2 and 14 at the end of the power stroke, permitting air to be blown through the engine cylinder. Gas from the engine cylinder discharges through exhaust ports 48 and 48 into exhaust manifold 50.

The pistons are maintained at from the center of the engine by one or more mechanisms which cause the pistons to move symmetrically toward and away from the center of the engine. Although only one mechanism is shown in detail, these mechanisms are preferably arranged in pairs on opposite sides of the engine cylinder.

The mechanism shown includes a pair of rods 52 and 54 connected to and extending from pistons l6 and 18, respectively, Each rod has :an integral plunger 56 or 58 and these plungers are slidable in parallel bores 68 and 62 in a housing 84. The rods extend beyond the plungers to provide equal areas on the ends of the plungers in small bores 66 and 8B in the housing. The adjacent ends of spaced bores and 62 are connected by passages Ill and 12 to permit a flow of fluid between the bores at each end. Bores 68 and 62 and passages 10 and 12 are filled with fluid so that the plungers 56 and 58 move symmetrically and cause the piston assemblies also to move sym metrically. T l i To compensate for leakage, fluid under pressure is directed continuously to the passages Ill and 12. A pump 14 delivers fluid from a sump 76 through similar conduits 18 and 19 to the pase sages l0 and 12, respectively. Orifices 80 and 81 may limit the flow of flu d into passages II! and 72. A pressure storage tank 82 maybe included in the fluid system. Between the ends of each of bores Ell and'62 area series of small discharge passages 84 and 85 through which fluid is discharged in small" quantity. The number, size and arrangement of passages 84 is duplicated by passages 86 so that when plungers 56 and 58 are sym metrical in the mechanism an equal number of passages in each bore will be covered. Any unsymmetrical movement of the plungers while the unit is operating will cause more discharge passages in one bore to be covered than are covered in the other bore so that a static pressure difference in the opposite bores is created to restore the plungers to symmetrical position. The passages 84 and 86 also allow flow of fluid through the device for cooling. Instead of orifices 80 and BI, it may be advantageous to use check valves, not shown, to prevent flow from passages 10 and 12 into conduits l8 and 19.

If the piston assemblies come to rest so that more discharge passages are covered by one plunger, a static pressure difference results which will move the plunger in the bore having the larger number of open discharge passages until equal distances equal numbers of passages 84 and 86 are covered.

Conduits 88 and 90 collect the fluid discharged from passages 84 and 86 and deliver it to the sump 16. Leakage from the ends of bores 66 and 68 is also collected by'these conduits. Sump 16 which may act as a settling and degassing tank may have a vent 92. The tank 82 may be used in the pressure lines to maintain desired pressures.

It is to be understood that the invention is' not limited to the specific embodiment herein i1- lustrated and described, but may beused incther ways without departure from itsspirit asdefined' by the'following claims.

I claim: H

1. A restraining mechanism for the opposed pistons of a free-piston unit including a rod extending from each piston, each rod having a double-acting plunger spacedzfrom the piston, a housing having spaced bores in which the; plungers are movable, conduits between adjoining ends of the bores, means for introducingfiuid under pressure to'each conduit, anda series ofports of small area in each bore adapted to be" uncovered and covered by the plungersiduring their-stroke.

2. A restraining mechanism for the opposed pistons of a free-piston'unit including a rod extendingfrom each piston,.each'rod havingia double-acting plunger spaced" from the piston, a housing having spaced bores in which the plungers are movable, conduits'between adjoining ends of thebores, means for introducing fluid under pressure to each conduit, and a series of ports of small area in each bore adapted to be uncovered and covered by the plungers during their stroke, said ports being spacedv axially of the here so that the ports are uncovered successively.

3. A restraining; mechanism for the opposed pistons of a free-piston unit including a rod extendingfrom each piston, each rodhaving a double-acting plunger spaced from the piston, a housing having spacedbores in which the mung-- ers. aremovable, conduits betweenadjoining ends of the: bores, means for introducing fluid under pressure? to each conduit, and a series of ports of small area in-each bore adapted to be uncovered and covered. by the plungers during their stroke, theports the opposed bores metrically arranged.

4rd restraining mechanism. for the opposed pistons of a free-piston. unit including. arod extending from each piston, each rod having a doubleacting1 plunger spaced. from the. piston, a housing. having. spaced. boresin which th plungbeing sym- 4 ers are movable, conduits between adjoining ends of the bores, means for introducing fluid under pressure to each conduit, and a series of ports of small area in each bore adapted to be uncovered and covered by the plungers during their stroke, the ports in the opposed bores being symmetrically arranged, and spaced axially from each other in each bore whereby the plungers uncover the ports successively.

5. A..restraining.mechanism for the opposed pistons; of. a free-piston engine-and-compressor unit, said mechanism including a pair of rods, one red. extending from each piston, a plunger on each rod,.. a 'housing having bores in which said plungersreciprocate, conduits between adjacent endsofthe. bores, said bores and conduits being filled with fluid, whereby movements of theplungers are synchronized, and means for venting each bore in proportion to the length of theplunger stroke. i

GUA. restraining mechanism. for the opposed pistons of a free-piston engine-and-compressor unit, said mechanism including a, pair. of. rods, one. rod extending from each piston, a plunger on each rod, a. housing having bores in which said plungers reciprocate, and conduits between adjacent ends of the. bores, and a means for maintaining asubstantially constant volume of fluid insaid bores and conduits. i

7. A restraining mechanism for the opposed pistons of a free-piston, engine-and-compressor unit, said mechanism. including a pair, of rods, one rod extending from each piston, a plunger on each. rod, a housing having bores in which said plungers reciprocate, and conduits. between adjacent. ends of the bores, and a means for maintaining asubstantially constant volume. of fluid in said bores and conduitssaid. meansineluding a source of fluid under pressure, means for directing,fluidfromsaid source to saidbores and conduits, and several discharge ports in each bore adapted to be uncovered successively by the plungers as-they reciprocate 8. A restraining mechanism. for. the opposed pistons of a free-piston engine.-and-compressor unit, said. mechanism including. a pair. of. rods, one rod extending from each piston, a plunger one eachrod, a housing having bores in which said plungers recipr.ocate,.and means for controlling the fluid pressures in said. boresfor causing the plungers to remainin symmetrical relation, including means for venting. said bore as theplungers reciprocate.

ANDREW SKY. 

